3.1 - A Battery and a Bulb

Vocabulary:


Circuit- Any complete path along which charge can flow.

In Series- Term applied to portions of an electric circuit that are connected in row so that the current that goes through one must go through all of them.

In Parallel- Term applied to portions of an electric circuit that are connected at two points and provide alternative paths for the current between those two points.

Series Circuit- An electric circuit in which devices are arranged so that charge flows through each in turn. If one part of the circuit should stop the current, it will stop throughout the circuit.

Parallel Circuit- An electric circuit in which devices are connected to the same two points of the circuit, so that any single device completes the circuit independently of the others.


Schematic Diagrams- Diagram that describes an electric circuit, using special symbols to represent difference devices in the circuit.


35.1 - A Battery and a Bulb


  • Circuits form a path between two terminals, and one of the simplest is a battery and a light bulb.

35.2 - Electric Circuits


  • Electricity flows if there is a continuous path for it, but if it is interrupted, the current is forced to stop.
  • More than one device can be part of the same circuit. If they flow through each device one after another, it is a series circuit. If there are multiple paths for the electricity, it is a parallel circuit.


35.3- Series Circuits


Characteristics of series circuits:
  • Single path through the circuit. When the current is interrupted at any point, the current stops.
  • The total equivalent resistance of the circuit is the sum of the resistances of each element.
  • The potential difference divided by the total resistance equals the current. The current in each element equals the total current in the circuit.
  • The voltage drop across each element is equal to the current times the element's resistance.
  • The voltage across the circuit is equal to the sum of the voltage drops across each element.


35.4- Parallel Circuits


Characteristics of parallel circuits:
  • The voltage across each element is the same because each element of a circuit connects the same two points.
  • The amount of current in each element is inversely proportional to the resistance of each element.
  • The total current in the circuit is equal to the sum of the currents through each element.
  • The total resistance will decrease as the number of parallel branches increases. The total resistance will be less than the resistance of any individual element.


35.5- Schematic Diagrams


Each part of a circuit has its own symbol that represents it. The diagram below shows the symbols for each aspect of a circuit.
IMG_0002.jpg
Taken from "Physics Review Notes" by Tom Strong



35.6 - Combining Resistors in a Compound Circuit


  • For a Series Circuit, the total resistance equals the sum of all the resistances:

>equation1.JPG
http://www.bartleby.com/images/A4images/A4series.jpg
http://www.bartleby.com/images/A4images/A4series.jpg

The series circuit above contains a power source (battery) and three resistors (light bulbs).
http://www.school-for-champions.com/science/images/dc_circuits-series.gif
http://www.school-for-champions.com/science/images/dc_circuits-series.gif

The series circuit above is a diagram of the picture of a series circuit earlier on the page. It contains a power source (battery) and three resistors (light bulbs).



  • For a Parallel Circuit, the inverse of the total resistance equals the sum of the inverse of all the resistors:
equation2.JPG

examples.JPG
http://www.wisc-online.com/objects/index_tj.asp?objID=DCE1502


  • http://www.bbc.co.uk/schools/ks3bitesize/science/images/sci_dia_56.gif
    http://www.bbc.co.uk/schools/ks3bitesize/science/images/sci_dia_56.gif
  • The illustration above shows that in a parallel circuit, if the current stops in one resistor it continues in the others.
  • http://people.sinclair.edu/nickreeder/EET114/PageArt/CircuitSeriesConnectST2.gif
    http://people.sinclair.edu/nickreeder/EET114/PageArt/CircuitSeriesConnectST2.gif
  • The diagram above shows a combination series and parallel circuit.

35.7- Parallel Circuits and Overloading

  • As more devices are added to a circuit, the total current increases.
  • The current can be more than the wires can safely handle, which fuses and circuit breakers prevent.